Monitoring and Modelling Salt-Marsh Accretion in Europe and South America

Predicted accelerated sea-level rise (SLR) for the present century and beyond will have a significant effect on the existence and distribution of coastal wetland habitats. For the U.S. coast, for example, many studies exist about potential habitat loss and degradation, whereas much less information is available on long-term trends for other parts of the world. Our main study areas are the European Wadden Sea in the southern North Sea and the estuary of the Rio de la Plata in between the coasts of Argentina and Uruguay.

While the European Wadden Sea is one of the most productive and dynamic coastal ecosystems in Europe with extensive mudflats and a considerable area of tidally influenced salt marshes, the Rio de la Plata is one of the largest estuaries in South America and strongly affected by the influence of El Niño/La Niña decadal oscillations and the impact of strong wind and storm tides. Salt marshes are found all along the estuary and are considered as highly important for the local biodiversity.

Besides their important ecological functions with their diverse flora and fauna, salt marshes have the ability of dissipating current and wave energy and therefore reducing erosional forces at dikes and unprotected coastal areas. In order to protect and restore salt marshes in coastal regions knowledge about processes that determine the accretion of organic and inorganic matter is essential for estimating future salt marsh gains or losses. Main physical drivers of wetland changes include tidal range, accommodation space, and the rate of SLR while strong storm events and variations of freshwater discharge into the system may also have major impacts.

Our research focuses on the collection of field data and the development and use of process-based salt-marsh and landscape models for studying the influence of these parameters on future wetland evolution and for providing timely information for nature conservation policy. We are aiming to: (i) identify the main physical drivers of salt marsh changes in our study areas; (ii) calibrate and validate the models with field data from our study sites; (iii) estimate future salt-marsh development under different scenarios of SLR, storm activity, freshwater discharge, and coastal protection.

Particular emphasis is given to site-specific model calibration and validation, as this is a major concern when modelling changes of coastal wetlands. Among other data, we employ radioisotope measurements of salt-marsh cores as a means to obtain important information on site-specific accretion rates and on the environmental conditions during which sedimentation takes place. Furthermorem, we investigate the local hydromorphological regimes in order to improve the model performances and to better understand how the processes in the foreshore of the marsh affect their accretion rates.

Schuerch M., Vafeidis A., Slawig T., Temmerman S. (2013) Modeling the influence of changing storm patterns on the ability of a salt marsh to keep pace with sea level rise. Journal of Geophysical Research Earth Surface, 118, pp. 84–96, doi:10.1029/2012JF002471.
Nolte S., Koppenaal E.C., Esselink P., Dijkema K.S., Schuerch, M., De Groot A.V., Bakker J.P., Temmerman S. (2013) Measuring sedimentation in tidal marshes: a review on methods and their applicability in bio-geomorphological studies. Journal of Coastal Cconservation, in press, doi:10.1016/j.ecss.2013.10.026.
Schuerch M., Rapaglia J., Liebetrau V., Vafeidis A., Reise K. (2012) Salt marsh accretion and storm tide variation: An example from a barrier island in the North Sea. Estuaries and Coasts, 35(2), pp. 486-500.

Coastal Wetlands and ASLR

Schuerch M., Vafeidis A., Slawig T., Temmerman S. (2013) Modeling the influence of changing storm patterns on the ability of a salt marsh to keep pace with sea level rise. Journal of Geophysical Research Earth Surface, 118, pp. 84–96, doi:10.1029/2012JF002471.
Nolte S., Koppenaal E.C., Esselink P., Dijkema K.S., Schuerch, M., De Groot A.V., Bakker J.P., Temmerman S. (2013) Measuring sedimentation in tidal marshes: a review on methods and their applicability in bio-geomorphological studies. Journal of Coastal Cconservation, in press, doi:10.1016/j.ecss.2013.10.026.
Schuerch M., Rapaglia J., Liebetrau V., Vafeidis A., Reise K. (2012) Salt marsh accretion and storm tide variation: An example from a barrier island in the North Sea. Estuaries and Coasts, 35(2), pp. 486-500.